Final answer:
Sympathetic preganglionic neurons originate from the thoracolumbar spinal cord, specifically from the T1-L2 regions. They activate postganglionic neurons using acetylcholine and are part of sympathetic responses that affect various organ systems throughout the body.
Step-by-step explanation:
Sympathetic preganglionic neurons arise from T1-L2, which covers all the thoracic spinal cord segments, and the first two lumbar spinal cord segments. This region is referred to as the thoracolumbar outflow or system. The sympathetic division of the autonomic nervous system impacts various organ systems through connections coming from this particular spinal region.
Preganglionic fibers emerge from the lateral horn and course through the ventral spinal roots to enter sympathetic chain ganglia or collateral ganglia. They release acetylcholine (ACh), which activates the ganglionic neuron via nicotinic receptors. Subsequently, the postganglionic axons release norepinephrine to adrenergic receptors on target effector organs, initiating broad sympathetic responses. There are certain exceptions in which ACh is released onto muscarinic receptors, such as in the sweat glands of the skin and blood vessels supplying skeletal muscles.
The sympathetic system's extensive influence is due, in part, to the specialized preganglionic connection to the adrenal medulla. This connection allows the release of hormones into the bloodstream, affecting many systems rapidly and concurrently.